"Data" in this context means some sort of weather data. Such data is often plotted on map-view (looking down on a surface) or cross-sections (looking at a pattern sideways). Knowing the different types of weather data and being able to decode and interpret them is key here.

"Importance" is often subjectively defined but to scientists is objectively defined.

Subjective: open to interpretation. To the average person, a pattern of importance could be the inland extent of fog during the summer